A group promoting sun safety says ultraviolet radiation levels are rising rapidly with the arrival of daylight saving on Sunday.
Sunsmart says while temperatures are still low, UV levels are now high enough to cause sunburn.
It says New Zealanders have the world's highest rates of melanoma skin cancer which kills 300 people each year.
Richard McKenzie, a principal radiation scientist at the National Institute of Water and Atmospheric Research, says UV is significantly more intense at the end of September than at the beginning.
Dr McKenzie says coming out of winter, people have pale skin which is more easily damaged by the sun.